The invention relates to a composition and method which are useful for removing certain impurities from certain organic liquids. More particularly, the invention relates to a composition and method which are useful for treating fats and oils, especially used fryer cooking oil.
During use, cooking oil has a tendency to decompose to some extent thereby forming fatty acids in the oil. In addition, the cooking oil picks up particulate and soluble contaminates and food juices from the food being fried. These impurities in the cooking oil cause certain undesirable properties in the used oil. Specifically, with a cooking oil which has been thus contaminated from use, the frying properties of the oil are degraded. For example, the food fried with such contaminated oil many times becomes too browned on the outside before it it properly cooked on the inside. Also, used cooking oil with certain contaminants of as low as 12 ppm resulting from food juices and/or the interaction of food juices with fatty acids, has a tendency to foam "or boil" while cooking, which is undesirable. In addition, with as little as 6 ppm of such contaminants, the used cooking oil tends to have oleophilic properties with food, thus leaving oily residues on the surface of the fried food product. All of these properties are normally considered undesirable.
Thus, a desirable cooking oil is one which produces a fried food product browned on the outside and properly cooked on the inside and which has oleophobic properties with food leaving the food with minimum oily residues on the surface of the food product. Moreover, if such a cooking oil could be quickly and economically obtained by treating contaminated used cooking oil to restore and/or maintain such desirable properties in the used cooking oil, it would be highly advantageous.
Various compositions and methods have been used in the past in attempts to remove impurities from fats and oils. For example, treated diatomaceous earth materials, i.e., synthetic silicates, have been recently marketed under the trade name "Micro Sweet Filter Aid" as materials to be added to used cooking oil for the removal of impurities therefrom. This material, however, requires the use of a filter cake.
A method for treating cooking oil is also disclosed in U.S. Pat. No. 3,947,602 in which the cooking oil is contacted with a food compatible acid, followed by separation of the oil and the acid prior to reuse of the oil. The method is said to increase the useful lifetime of the cooking oil. A porous pumicite filter aid is disclosed in U.S. Pat. No. 3,996,158. This porous pumicite material is said to be useful for washing dry cleaning solvents so as to retain a low ratio of non-volatile matter therein.
The compositions discussed above for the treatment of fats and oils have certain disadvantages. For example, compositions employing activated carbon are hard to filter thoroughly, making it difficult to remove the material from treated oil with facilities normally available in a restaurant kitchen. Others of the above methods require the use of a filter cake with a filter machine to accomplish the filtering step, while others do not provide maximum removal of impurities from the used cooking oil. Still others require long time periods for treatment which make them economically disadvantageous. Therefore, it would be very desirable to provide a composition overcoming these disadvantages and having the ability to remove undesirable impurities from and to restore desirable cooking properties to used cooking oil, which composition could be simply added to the hot, contaminated cooking oil and thereafter filtered from the cooking oil in an economically suitable time without the need for the formation of a filter cake with a filter machine.